Randolph Water Hardness & Quality Report (2026)

The Randolph-Holbrook Joint Water Board serves Randolph Town and Holbrook in Norfolk County, Massachusetts, providing drinking water to approximately 35,000 residents across 20 square miles. Primary sources include surface water from the Neponset River Reservoir (including the Koch-Reissig Reservoir) and groundwater from wells in the local glacial aquifer. Treatment at the Board's facilities includes filtration, disinfection with chloramines, and corrosion control. The system is regulated by the Massachusetts Department of Environmental Protection and complies with EPA standards, with annual Consumer Confidence Reports detailing testing results.

The supply originates in the Neponset River watershed, spanning urban and suburban areas south of Boston with forested uplands. Underlying geology features hard metamorphic rocks of the Avalonian terrane — slate, argillite, and granite from the Late Proterozoic to Paleozoic eras — fractured and overlain by Quaternary glacial deposits. These sands and gravels form productive aquifers that impart a moderately mineralized character through contact with limestone fragments and mafic minerals, while surface waters pick up ions from soil leaching, yielding a soft to moderately hard profile without extreme mineral loading.

At this soft water level, scale buildup is minimal, sparing dishwashers, washing machines, and water heaters from significant calcium deposits. Soap lathers easily, reducing detergent use, but low mineral content may accelerate pipe corrosion, potentially increasing lead or copper leaching in older homes. Routine maintenance involves checking fixtures for wear rather than descaling; a water softener is optional and generally not recommended. The 2022 CCR shows pH averaging 9.5, full compliance with lead and copper rules, haloacetic acids up to 20 ppb, and trihalomethanes up to 45 ppb — both under MCLs. No PFAS exceedances were noted, though monitoring continues amid regional concerns.